Introduction

The HIV epidemic has stabilized in South Africa, but at an unacceptably high national prevalence rate of 11% [1] with some sub-populations continuing to be more at risk of contracting HIV than others. Young women aged 15–24 are one such sub-population, as they account for 90% of all new HIV infections in their age group [2]. Further, HIV prevalence among young women increases dramatically with age: 7% among 15–19 year olds compared to 21% among 20–24 year olds and 33% among 25–29 year-olds [1]. This three- to four-fold increase in HIV prevalence among young women as they grow older demonstrates their escalating vulnerability to HIV. Owing to these HIV transmission dynamics among women aged 20–29, they have been classified as a most at risk population (MARP) [1]. Further, HIV prevalence amongst females aged 15–24 years is three to four times higher than among males of similar age [1]. Clearly, there are sustained age and sex variations in HIV transmission among young people in the country.

Structural factors such as women’s socio-economic status and gender disempowerment contribute to women’s heightened vulnerability to HIV in South Africa [3]–[5]. In addition, studies in the region point to the high prevalence of sexual risk behaviors among young women, such as early sexual debut, transactional sex, age mixing and low to no condom use [6]–[9] to explain women’s vulnerability to HIV. However, none of these studies have been conducted among women who have multiple sexual partners; a risk behavior considered to heighten the risk of HIV in the region.

Multiple sexual partnering increases the likelihood of concurrency because the more sexual partners one acquires in a short space of time, the greater the likelihood of partner overlap [10], [11]. Although not incontrovertible [12], [13], evidence suggests that concurrency is a key driver of the epidemic in sub-Saharan Africa. In high HIV prevalence settings, the density of concurrent sexual networks increases the chance that an uninfected sexual partner will encounter an acutely HIV infected sexual partner (with high viral load and greater infectivity) during an unprotected sexual act in the sexual network [10], [14]–[16].

While an association between concurrency and low condom use has been found amongst women aged 18–50 in the USA [15], it is not known whether and to what extent women who have multiple sexual partners in Sub-Saharan Africa also engage in other risk behaviors such as transactional sex (where sex is exchanged for cash or material goods), age mixing (where young women have much older male sexual partners) or inconsistent condom use. And yet, multiple sexual partnering is of little epidemiological relevance for the spread of HIV infections if all partners in these sexual networks use condoms consistently.

We aimed to assess the prevalence of sexual risk behaviors and HIV and the predictors of inconsistent condom use among young women with MSP in a peri-urban setting in South Africa.

Methods

Data Analysis

Estimates of population proportions and 95% confidence intervals (CIs) for demographics and risk behaviors were calculated using the Respondent-Driven Sampling Analysis Tool version 5.6 (RDSAT) (Table 1). This software package enables analyses of equilibrium, and generates sample weights to take into account differential recruitment (homophily) and variations in participants’ network sizes [19].

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Table 1. Sample & population estimates of demographic characteristics and sexual risk behaviors.

https://doi.org/10.1371/journal.pone.0051998.t001

A sample attains equilibrium when the sample distribution on key variables remains stable even as new individuals are added to the sample [19], [20], [21]. Equilibrium was reached between 2 and 3 waves on key variables such as age, poverty status, HIV status, inconsistent condom use with main and casual partners, male partner infidelity, transactional sex, concurrency and age mixing.

Homophily index values that are large (1+) suggest that recruiters had a greater preference for in-group recruitment; small index values (−1) indicate preference for out-group recruitment, whilst index values close to 0 suggest neither in-group, nor out-group recruitment patterns, thereby overcoming recruitment biases [20], [21]. In this study the homophily index (Hx) values for key variables ranged from −0.396 to 0.186. Hx by HIV status revealed that cross recruitment occurred among networks of HIV positive (Hx = 0.093) and HIV negative (Hx = 0.08) participants.

To determine the personal network size of each participant, we asked the following: “How many women do you know (i.e. you know their name and they know yours); you have seen them in the past three months; they are 16–24 years old; they live/work/socialize in the study community and they have had sex with more than one man in the past three months?” The personal network sizes of the participants ranged from 2 to 80 with a mean of 6.

Bivariate analyses were performed with inconsistent and no condom use as the main outcomes. To assess the predictors of inconsistent and no condom use, multivariate logistic regression models (Table 2) were constructed in STATA 10.10 using backward stepwise regression methods [24]. Individualized weights generated on the outcome variables by RDSAT 5.6 were imported and included in each of the final logistic regression models.

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Table 2. Multivariate logistic regression models showing predictors of inconsistent condom use and no condom use.

https://doi.org/10.1371/journal.pone.0051998.t002

We also conducted Mantel-Haenszel tests for homogeneity to determine if transactional sex modifies the interaction between inconsistent condom use with casual partners and concurrency.

The DBS were analyzed at a referral laboratory for anonymous HIV testing where serum was eluted from samples and tested and re-tested with a 4th generation HIV ELISA (Vironostika Uniform II plus 0) and a 3rd generation (antibody only) HIV ELISA (SD Bioline). Samples that were reactive in both assays were reported as positive. Discordant samples were tested by western blot (HIV1/2 Biorad).

Results

All young women reported sexual relations with a main partner, an average of 7 male sexual partners in the past three months and a very high proportion (87%, CI 77.0–87.7) reported concurrency within these sexual relationships. Table 1 shows the prevalence of sexual risk behaviors. Despite the fact that 73% (CI 67.6–78.4) reported easy access to condoms at shebeens, the majority reported inconsistent condom use both with their most recent main partner (77%, CI 72.4–82.7) and casual sexual partners (56%, CI 49.6–62.1) in the past three months. Among those who reported having sex with once off partners in the past three months (82%, CI 64.3–95.9), 30% (CI 17.1–31.3) did not use a condom at last sex with their most recent once off partner.

More than 9 out of 10 young women (91%, CI 91.2–96.6) reported that they had engaged in transactional sex with their most recent sexual partner. More than one third (34%, CI 31.2–36.7) reported early sexual debut (<15 years old), 59% (CI 55.2–47.7) reported age mixing and 72%, (CI 61.1–76.6) knew or suspected their main partner to have other sexual partnerships (male partner infidelity). Most of the respondents were aged 16–19 (74%, CI 68.0–81.0), with 21% (CI 16.9–27.2) reporting abject poverty.

Women who reported a high number of multiple casual sexual partners (five or more casual partners in the past three months), were also significantly more likely to have unsafe sex (inconsistent condom use) both with their casual partners (OR 2.43, CI 1.39–4.25), and with their most recent main partner (OR 2.22, CI 1.07–4.60), compared to those with fewer partners (Table 2). Transactional sex did not modify the interaction between inconsistent condom use with casual partners and concurrency (crude OR 1.93, CI 0.94–3.95; adjusted OR 1.93, CI 0.94–3.96).

The youngest women (aged 16–19) were more likely to not have used a condom at last sex with the last once-off partner (OR 4.37, CI 1.67–11.41) compared to older women (aged 20–24). Early sexual debut (<15 years) was also marginally associated with the likelihood of not using condoms at last sex with this type of partner (OR 1.90, CI 0.91–3.94). Women reporting easy access to condoms at shebeens were 55% less likely to not have used condoms at last sex with their most recent once off partner (OR 0.45, CI 0.20–0.97).

The prevalence of HIV was three times higher among women aged 20–24 (12%; CI 5.3–22.0) than among women aged 16–19 (4%, CI 1.4–7.3). Average HIV prevalence across age groups was 5% (CI 4.1–6.5).

Discussion

This is the first study in South Africa to be conducted among a heterosexual, young female subpopulation who self-report having multiple sexual partners. In this township sub-population, we found a strikingly high prevalence of high-risk behaviors for HIV. Despite the fact that the majority were still in school and less than a quarter reported abject poverty, most young women had engaged in transactional sex, and practiced unsafe sex with concurrent, considerably older partners, many of whom also had other sexual partners.

In a context where strict monogamy is considered the exception rather than the rule [25]–[27] and where material rewards are generally considered a common feature of successful sexual relationships [25], [27], [28] classifying women who have multiple sexual partners and comparing them to other groups in South Africa is complex. First, despite the high number of partners and the high prevalence of transactional sex among them, this subpopulation cannot be simply classified as commercial sex workers (CSWs) [3], [28], [29]. Two studies that have measured sexual risk among commercial, female sex workers in Pretoria [30] and in Johannesburg [31], report dynamics of risk that may be similar to what we found among our subpopulation: a similarly high prevalence of inconsistent condom use with main partners (59%) in spite of almost half (41%) of the population of CSWs reporting male partner infidelity [30] and levels of condom use with clients (85%) [31], comparable to what was reported for condom use at last sex with once off partners in our study. However, and importantly, despite these similarities, the terms and conditions of the sexual exchange are organized differently in the two groups, resulting in different opportunities for safer sex negotiations. Among young women who have multiple sexual partners, the exchange of monetary rewards occurs in the context of romantic relations, often after sexual intercourse has taken place and relies on implicit and symbolic rather than explicit communications about the type and price of the sex act [3], [27], [32], [33]. The absence of an empowering context that allows for explicit and upfront negotiations about the type and cost of sexual encounters prior to the sex act means that young women who are in transactional sexual relationships of this kind are constrained in their ability to proactively determine the sexual [safety] terms of the sexual act [29], [32]. This is perhaps one area where CSWs, who negotiate sex for exchange encounters preliminarily and explicitly, are positioned advantageously to women who engage in transactional sex. These differences are important to emphasize if appropriate and tailored intervention strategies are to be developed for women who engage in transactional sexual relationships, particularly as this risk behavior is more common in peri-urban settings than commercial sex work [27].

Clearly the practice of transactional sex is not untouched by the prevailing gender norms that undermine women’s sexual and reproductive health in the country [27]. However, transactional sex should not be simply reduced to a behavior where women are construed as mere passive victims who have no opportunities for agency and enactments of empowerment in their relationships [30], [31], [41], [4]. An important question regarding displays of agency is whether they translate to empowerment that is sexually protective and meaningful for HIV risk reduction among young women [34].

Further, the high prevalence of transactional sex in a context where more than two thirds of the population are classified as poor and non-poor rather than abjectly poor, suggests that the popularity of the risk behavior may have more to do with wealth inequalities than abject poverty [28], [35].

Together, these findings emphasize the need for a more nuanced understanding of transactional sex; one that clearly distinguishes transactional sex from commercial sex work, leading to interventions that are better equipped to deal with the complexity of this risk behavior and its driving factors.

The high number of sexual partners observed among the young women may be indicative of the multiplicity of young women’s needs [25], which may not be sufficiently met by main, single partnerships. This proposition is particularly compelling in light of emerging evidence that young women’s main partnerships in South Africa may be socially structured to be “traditional” [34], with emphasis on enactments of masculinities and femininities that encourage male partners to be dominant, controlling, and emotionally reserved, whilst requiring women to be sexually timid, submissive and tolerant of their main partners’ misbehavior. Thus young women may be acquiring various sexual partners, to meet multiple needs, be it love, sexual pleasure, material rewards or insurance against abandonment by their current main sexual partner [25], [28]. Interventions that target this subpopulation need to take into account the ways in which social beliefs about men and women’s roles in their intimate steady relationships configure the size and function of their multiple partnerships.

Together with the high levels of inconsistent condom use, multiple sexual partnering and concurrency, the reported high prevalence of male partner infidelity may lead to very densely populated sexual networks, otherwise known as “concurrency superhighways” [17], which facilitate a wider spread of HIV [16]. Further, the highly significant association between inconsistent condom use and a high number of partners in a short period of time suggests that multiple sexual partnering creates a fertile environment for unsafe sexual practices. The finding also highlights the importance of interventions that emphasize partner reduction among populations where multiple sexual partnering is a norm.

The high prevalence of age mixing among our study participants could explain the low use of condoms. Older men often take on a dominant position in age-asymmetrical relationships [7]–[9] and are known to use their age (and economically) related power to undermine young women’s preferences for safer sex [5], [7]. This is particularly concerning in a context where the prevalence of HIV has been shown to increase drastically among older men, suggesting that when young women establish unprotected sexual contacts with this group they are essentially entering and mixing with a high HIV seroprevalence pool [1], [2], [36]. Thus, interventions that reduce the prevalence of age mixing could significantly reduce the prevalence of HIV among young women [37].

Notably, women who reported easy access to condoms in alcohol serving venues were more likely to use condoms with once off partners. This is an indication of the large gains to be made if condom availability is extended to spaces where young people socialize and where transactional sexual relationships are initiated.

The drastic increase in HIV infections among women aged 20–24 compared to those aged 16–19 in our sample mirrors the trend observed in national household survey data, which show a relatively low prevalence of HIV for women under 20 years of age (7% among 15 - 19 year olds), but a three-fold increase among women aged 20–24 (21%) [1]. These findings highlight that much can be done to prevent HIV in this subpopulation if interventions target women earlier, specifically when they are young adolescents. Further, the overall HIV prevalence of 5%, whilst almost double the provincial prevalence of 3% among youth aged 15–24 [1], supports emerging evidence that suggests that high-risk behaviors do not necessarily translate to a high prevalence of HIV in low prevalence settings [38].

We deliberately recruited women who self-reported multiple sexual partnering because of the strong hypothesized link between this behavior and HIV prevalence and gaps in knowledge about this and concomitant risk behaviors in the Sub Saharan African region. While multiple sexual partnering is common among women in the general population [25], [10], current national household surveys provide limited knowledge about this high-risk behavior. As such, what we know about women who have multiple sexual partners is based on knowledge derived from qualitative studies but rarely confirmed through quantitative enquiries. Thus, whilst conclusions about the extent to which our subpopulation is representative of all women who have multiple sexual partners should be made cautiously, these results make an important contribution to our understanding of this risk group. They show not only that these women have high numbers of partners, but that they also engage in a range of other high risk behaviors such as transactional sex and age mixing, whilst foregoing consistent condom use with their various sexual partners, making them a high risk group for HIV infection.

Supporting Information